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Abstract:

A fuel cell stack includes a stacked body, a first terminal plate, a
first insulating plate, a first end plate, and a first insulating collar
member. The first insulating collar member includes a first tubular
portion and a first flange portion. The first tubular portion is provided
in the first fluid manifold hole. The first flange portion is disposed at
one end of the first tubular portion. Another end of the first tubular
portion projects to an outside of the first fluid manifold hole and is in
slidably contact with an inner circumferential surface of the first outer
manifold member via an outer circumferential surface sealing member. The
first flange portion is in contact with the first insulating plate via an
end-face sealing member.

Claims:

1. A fuel cell stack comprising: a stacked body including a plurality of
fuel cells which are stacked in a stacking direction, each of the fuel
cells comprising: an electrolyte-electrode assembly having a pair of
electrodes and an electrolyte disposed between the pair of electrodes in
the stacking direction; and a pair of separators between which the
electrolyte-electrode assembly is sandwiched in the stacking direction; a
first terminal plate provided at a first end of the stacked body in the
stacking direction; a first insulating plate provided at the first end of
the stacked body in the stacking direction; a first end plate provided at
the first end of the stacked body in the stacking direction, the first
end plate including a first fluid manifold hole; and a first insulating
collar member comprising: a first tubular portion through which one of a
cooling medium and a reactant gas is to flow to a first outer manifold
member in the stacking direction, the first tubular portion being
provided in the first fluid manifold hole; and a first flange portion
disposed at one end of the first tubular portion, another end of the
first tubular portion projecting to an outside of the first with an inner
circumferential surface of the first outer manifold member via an outer
circumferential surface sealing member, the first flange portion being in
contact with the first insulating plate via an end-face sealing member.

2. The fuel cell stack according to claim 1, further comprising: a spacer
member provided between the first end plate and the first insulating
plate to adjust a thickness of the fuel cell stack in the stacking
direction.

3. The fuel cell stack according to claim 1, further comprising: a second
terminal plate provided at a second end of the stacked body in the
stacking direction, the second end being opposite to the first end with
respect to the stacked body in the stacking direction; a second
insulating plate provided at the second end of the stacked body in the
stacking direction; and a second end plate provided at the second end of
the stacked body in the stacking direction.

4. The fuel cell stack according to claim 3, further comprising: a spacer
member provided between the second end plate and the second insulating
plate to adjust a thickness of the fuel

5. The fuel cell stack according to claim 3, wherein the second end plate
includes a second fluid manifold hole.

6. The fuel cell stack according to claim 5, further comprising: a second
insulating collar member comprising: a second tubular portion through
which one of a cooling medium and a reactant gas is to flow to a second
outer manifold member in the stacking direction, the second tubular
portion being provided in the second fluid manifold hole; and a second
flange portion disposed at one end of the second tubular portion, another
end of the second tubular portion projecting to an outside of the second
fluid manifold hole and being in slidably contact with an inner
circumferential surface of the second outer manifold member via an outer
circumferential surface sealing member, the second flange portion being
in contact with the second insulating plate via an end-face sealing
member.

[0005] For example, a solid polymer electrolyte fuel cell includes a power
generation cell, in which an electrolyte membrane-electrode assembly
(MEA) is sandwiched between a pair of separators, the electrolyte
membrane-electrode assembly including an electrolyte membrane formed of a
polymer ion exchange membrane, and anode and cathode electrodes that are
disposed on both sides of the electrolyte membrane. A fuel cell stack, in
which a predetermined number (for example, hundreds) of power generation
cells are usually stacked, is used as an in-vehicle fuel cell stack, for
example.

[0006] In the above-described fuel cell, a fuel gas passage for passing a
fuel gas to the anode electrode is provided on the surface of one of the
separators, and an oxidant gas passage for passing an oxidant gas to the
cathode electrode is provided on the surface of the other of the
separators. In addition, a cooling medium passage for passing a cooling
medium is disposed between adjacent power generation cells or between
adjacent cells in a predetermined number of power generation cells along
the surface direction of the separators.

[0007] In some fuel cells, a fuel gas supply communication hole which
supplies a fuel gas to a fuel gas passage, a fuel gas discharge
communication hole which discharges a consumed fuel gas from the fuel gas
passage, an oxidant gas supply communication hole which supplies an
oxidant gas to an oxidant gas passage, an oxidant gas discharge
communication hole which discharges a consumed oxidant gas from the
oxidant gas passage, a cooling medium supply communication hole which
supplies a cooling medium to a cooling-medium passage, and a cooling
medium discharge communication hole which discharges a used cooling
medium from the cooling medium passage are formed as through holes in the
stacking direction, i.e., a so-called internal manifold is formed.

[0008] In this type of internal manifold mold fuel cell, a connecting
structure for communicating each communication hole to an external
manifold member is used in at least one of the end plates. For example,
the fuel cell disclosed in Japanese Unexamined Patent Application
Publication No. 2005-259427 includes a stacked body of the cells 1 as
illustrated in FIG. 9. A terminal 2, an insulator 3, and a pressure plate
4 are disposed at one end of the structure of stacked body of the cells
1.

[0009] The cell 1 has a MEA5, on both sides of which a first separator 6
and a second separator 7 are disposed, respectively. A conduit member 8
has a tube portion 8b which penetrates through a hole of the pressure
plate 4, and has a flange 8a on the side of the pressure plate 4 that
faces the stacked body. The flange 8a is housed in a housing portion of
the terminal 2 and the insulator 3, and is connected via an end-face seal
9 to the stacked body of the cells 1 as a passage.

SUMMARY OF THE INVENTION

[0010] According to one aspect of the present invention, a fuel cell stack
includes a stacked body, a first terminal plate, a first insulating
plate, a first end plate, and a first insulating collar member. The
stacked body includes a plurality of fuel cells which are stacked in a
stacking direction. Each of the fuel cells includes an
electrolyte-electrode assembly and a pair of separators. The
electrolyte-electrode assembly has a pair of electrodes and an
electrolyte disposed between the pair of electrodes in the stacking
direction. The electrolyte-electrode assembly is sandwiched between the
pair of separators in the stacking direction. The first terminal plate is
provided at a first end of the stacked body in the stacking direction.
The first insulating plate is provided at the first end of the stacked
body in the stacking direction. The first end plate is provided at the
first end of the stacked body in the stacking direction. The first end
plate includes a first fluid manifold hole. The first insulating collar
member includes a first tubular portion and a first flange portion. One
of a cooling medium and a reactant gas is to flow through the first
tubular portion to a first outer manifold member in the stacking
direction. The first tubular portion is provided in the first fluid
manifold hole. The first flange portion is disposed at one end of the
first tubular portion. Another end of the first tubular portion projects
to an outside of the first fluid manifold hole and is in slidably contact
with an inner circumferential surface of the first outer manifold member
via an outer circumferential surface sealing member. The first flange
portion is in contact with the first insulating plate via an end-face
sealing member.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] A more complete appreciation of the invention and many of the
attendant advantages thereof will be readily obtained as the same becomes
better understood by reference to the following detailed description when
considered in connection with the accompanying drawings.

[0012]FIG. 1 is a partially exploded perspective view of a fuel cell
stack according to a first embodiment of the present disclosure.

[0013]FIG. 2 is a schematic cross-sectional view of the fuel cell stack.

[0014]FIG. 3 is an exploded perspective view of the main part of a fuel
cell included in the fuel cell stack.

[0015]FIG. 4 is an exploded perspective view of the main part of the
vicinity of one end plate included in the fuel cell stack.

[0016]FIG. 5 is a cross-sectional view of the vicinity of the one end
plate, taken along a line V-V in FIG. 4.

[0017]FIG. 6 is an exploded perspective view of the main part of the
vicinity of the other end plate included in the fuel cell stack.

[0018]FIG. 7 is a cross-sectional view of the vicinity of the other end
plate, taken along a line VII-VII in FIG. 6.

[0019]FIG. 8 is a perspective view of an insulating collar member
included in a fuel cell stack according to a second embodiment of the
present disclosure.

[0020]FIG. 9 is a cross-sectional view of the fuel cell which is
disclosed in Japanese Unexamined Patent Application Publication No.
2005-259427.

DESCRIPTION OF THE EMBODIMENTS

[0021] The embodiments will now be described with reference to the
accompanying drawings, wherein like reference numerals designate
corresponding or identical elements throughout the various drawings.

[0022] As illustrated in FIGS. 1 and 2, a fuel cell stack 10 according to
a first embodiment of the present disclosure serves as an in-vehicle fuel
cell stack which is mounted in, for example, a fuel cell vehicle (not
illustrated) such as a fuel cell electric vehicle.

[0023] The fuel cell stack 10 is a stacked body 13 which is formed by
stacking a plurality of fuel cells 12 in an arrow A direction (horizontal
direction). It is to be noted that the plurality of fuel cells 12 may be
stacked in an arrow C direction (vertical direction). As illustrated in
FIG. 2, a terminal plate 14a, an insulating plate 16a, and an end plate
18a are disposed at one end of the stacked body 13 in the stacking
direction. A terminal plate 14b, an insulating plate 16b, and an end
plate 18b are disposed at the other end of the stacked body 13 in the
stacking direction.

[0024] Recesses 16au, 16bu are formed in the insulating plates 16a, 16b,
and the terminal plates 14a, 14b are housed in the recesses 16au, 16bu.
Terminals 17a, 17b respectively extend from the terminal plates 14a, 14b
in the stacking direction, and the terminals 17a, 17b are exposed to the
outside from the end plates 18a, 18b (see FIG. 1). A thickness adjusting
spacer member (shim member) 19 for adjusting a clamping force applied to
the stacked body 13 in the stacking direction is interposed between the
end plate 18a and the insulating plates 16a (see FIG. 2).

[0025] As illustrated in FIG. 3, each fuel cell 12 is formed by
sandwiching an electrolyte membrane-electrode assembly (MEA) 20 between a
first separator 22 and a second separator 24. The first separator 22 and
the second separator 24 having elongated shape are each made of, for
example, a steel plate, a stainless steel plate, an aluminum plate, a
plated steel plate, or a metal plate received the surface treatment
against corrosion. The first separator 22 and the second separator 24
each have a surface which is rectangular and is formed to have a
corrugated cross section which is obtained by performing press working on
a thin metal plate. It is to be noted that the first separator 22 and the
second separator 24 each may be a carbon separator, for example.

[0026] At the upper-end of the fuel cells 12 in an arrow C direction (the
vertical direction in FIG. 3), an oxidant gas supply communication hole
26a for supplying an oxygen containing gas, for example, an oxidant gas,
and a fuel gas supply communication hole 28a for supplying a fuel gas,
for example, a hydrogen containing gas are arranged and disposed in the
arrow B direction (horizontal direction) so as to communicate with the
fuel cells 12 in the arrow A direction which is the stacking direction.

[0027] At the lower-end of the fuel cells 12 in the arrow C direction, an
oxidant gas discharge communication hole 26b for discharging an oxidant
gas, and a fuel gas discharge communication hole 28b for discharging a
fuel gas are arranged and disposed in the arrow B direction so as to
communicate with the fuel cells 12 in the arrow A direction. The oxidant
gas supply communication hole 26a, the oxidant gas discharge
communication hole 26b, the fuel gas supply communication hole 28a, and
the fuel gas discharge communication hole 28b each have an opening which
is approximately triangular (or approximately trapezoidal) in shape,
however, the opening is not limited to this, and may be, for example,
rectangular, polygonal, oval, or elliptical in shape.

[0028] Cooling medium supply communication holes 30a for supplying a
cooling medium, and cooling medium discharge communication holes 30b for
discharging a cooling medium are respectively disposed, for example, at
upper and lower positions of both ends of the fuel cells 12 in the arrow
B direction. A pair of the cooling medium supply communication holes 30a,
and a pair of the cooling medium discharge communication holes 30b each
have an opening which is rectangular in shape, however, the opening is
not limited to this, and may be, for example, oval, or elliptical in
shape.

[0029] A surface 22a of the first separator 22 that faces the electrolyte
membrane-electrode assembly 20 is provided with an oxidant gas passage 32
which communicates with the oxidant gas supply communication hole 26a and
the oxidant gas discharge communication hole 26b. The oxidant gas passage
32 allows an oxidant gas to flow in the arrow C direction below.

[0030] A surface 24a of the second separator 24 that faces the electrolyte
membrane-electrode assembly 20 is provided with a fuel gas passage 34
which communicates with the fuel gas supply communication hole 28a and
the fuel gas discharge communication hole 28b. The fuel gas passage 34
allows a fuel gas to flow in the arrow C direction below.

[0031] When the fuel cells are disposed adjacent each other the space
formed between the surface 22b of the first separator 22, and the surface
24b of the second separator 24 is provided for a cooling medium passage
36 which communicates with the cooling medium supply communication hole
30a and the cooling medium discharge communication hole 30b. The cooling
medium passage 36 allows a cooling medium to flow in the arrow C
direction below, and buffer portions (in an embossed form) 38a, 38b are
respectively provided above and below (upstream and downstream) the
cooling medium passage 36.

[0032] A first sealing member 40a is provided separately or integrally
with the surfaces 22a, 22b of the first separator 22, and a second
sealing member 40b is provided separately or integrally with the surfaces
24a, 24b of the second separator 24. As the material for the first
sealing member 40a and the second sealing member 40b, a sealing material,
a cushioning material, or a packing material, such as EPDM, NBR, a
fluoride rubber, a silicone rubber, a fluoro silicone rubber, a butyl
rubber, a natural rubber, a styrene rubber, a chloroprene or acrylic
rubber is used.

[0033] The electrolyte membrane-electrode assembly 20 includes, for
example, a solid polymer electrolyte membrane 42 which is a thin
perfluoro sulfonic acid membrane impregnated with water, and a cathode
electrode 44 and an anode electrode 46 between which the solid polymer
electrolyte membrane 42 is sandwiched.

[0034] The cathode electrode 44 and the anode electrode 46 each have a gas
diffusion layer which is formed of carbon paper or the like, and an
electrode catalyst layer which is formed by uniformly coating the surface
of the gas diffusion layer with porous carbon particles which carry
platinum alloy on the surfaces thereof. The electrode catalyst layer is
formed on the both sides of the solid polymer electrolyte membrane 42.

[0035] As illustrated in FIG. 1, a plurality of connecting members 50 are
spanned between the end plate 18a and the end plate 18b. The connecting
member 50 has a elongated plate shape, and two pieces of the connecting
member 50 are disposed on each of the longer side surfaces of the fuel
cell stack 10, and one piece of the connecting member 50 is disposed on
each of the shorter side surfaces of the fuel cell stack 10. Both ends of
the connecting members 50 in the arrow A direction are fixed to the
lateral sides of the end plate 18a and the end plate 18b by bolts 52.

[0036] A predetermined fastening load is applied between the end plates
18a and 18b in the stacking direction, and the distance between the end
plates 18a and 18b is maintained at a constant value.

[0037] As illustrated in FIG. 4, a cooling medium supply manifold hole
(fluid manifold hole) 54a which communicates with a pair of the cooling
medium supply communication holes 30a, and a cooling medium discharge
manifold hole (fluid manifold hole) 54b which communicates with a pair of
the cooling medium discharge communication hole 30b are formed in the end
plate 18a. Similarly, a pair of the cooling medium supply manifold hole
56a and a pair of the cooling medium discharge manifold hole 56b are
formed in the spacer member 19.

[0038] As illustrated in FIGS. 1 and 4, in the end plate 18a and spacer
member 19, an insulating collar member 58a is arranged to be inserted
through in the cooling medium supply manifold holes 54a, 56a, and an
insulating collar member 58b is arranged to be integrally inserted in the
cooling medium discharge manifold holes 54b, 56b.

[0039] As illustrated in FIGS. 4 and 5, the insulating collar member 58a
integrally has a tubular portion 60 to be inserted in the cooling medium
supply manifold holes 54a, 56a, and a flange portion 62 with a large
dimension provided at one end of the tubular portion 60. The tubular
portion 60 has an oval shape or an elliptical shape corresponding to the
inner shape of the cooling medium supply manifold holes 54a, 56a, and is
disposed with a space secured in the cooling medium supply manifold holes
54a, 56a. It is to be noted that the tubular portion 60 may be in direct
contact with the inner surface of the cooling medium supply manifold
holes 54a, 56a.

[0040] An front end 60a of the tubular portion 60 is exposed to the
outside from the outer surface of the end plate 18a, and an O-ring (outer
circumferential surface sealing member) 64, which is a radial seal, is
arranged and disposed along a circumferential groove 60ad on the outer
circumference of the front end 60a. The O-ring 64 has an oval shape or an
elliptical shape. It is to be noted that the O-ring 64 may be disposed
in, for example, a groove 72d which is formed on the inner
circumferential surface of the below-described cooling medium supply
manifold 72 (see FIG. 5).

[0041] At least one, for example, two positioning holes 66 are formed in
the flange portion 62. A positioning pin 68 is inserted in each of the
positioning holes 66, and is inserted through in a positioning hole 70a
and a positioning hollow 70b which are respectively formed in the spacer
member 19 and the end plate 18a. An end-face seal 71 may be provided
between the end face of the flange portion 62 and the insulating plate
16a.

[0042] As illustrated in FIG. 5, the flange 62 of the insulating collar
member 58a is in contact with the end face of the spacer member 19, and
is pressed and held against the insulating plate 16a, for example, by the
second sealing member (end face sealing member) 40b of the second
separator 24.

[0043] The insulating collar member 58b is formed similarly to the
above-described insulating collar member 58a. The same components are
labeled with the same reference symbols, and detailed description thereof
are omitted.

[0045] The cooling medium supply manifold 72 has a downward U shape, and
on both right and left ends, connecting holes 72a are respectively
provided, in each of which the front end 60a of the tubular portion 60
provided in the insulating collar member 58a fits. The connecting hole
72a has an opening with an oval or elliptical cross section, and the
inner circumferential surface of the connecting hole 72a is in contact
with the O-ring 64, and thus the tubular portion 60 is slidably disposed
(see FIG. 5) against the connecting hole 72a.

[0046] A screw 76 is inserted in a hole 72c which is formed in a flange
portion 72b provided on the outer circumference of the cooling medium
supply manifold 72, and the end of the screw 76 is screwed in a tapped
hole 78 formed in the end plate 18a (see FIGS. 4 and 5).

[0047] Similarly to the cooling medium supply manifold 72, the cooling
medium discharge manifold 74 is provided with connecting holes 74a, in
each of which the front end 60a of the tubular portion 60 provided in the
insulating collar member 58b fits as illustrated in FIG. 1. A screw 76 is
inserted in a hole 74c which is formed in a flange portion 74b provided
on the outer circumference of the cooling medium discharge manifold 74,
and the end of the screw 76 is screwed in a tapped hole 78 formed in the
end plate 18a.

[0050] In the end plate 18b, insulating collar members 84a and 84b are
arranged to be inserted in the oxidant gas supply manifold hole 80a and
the oxidant gas discharge manifold hole 80b, respectively, and insulating
collar members 86a and 86b are arranged to be inserted in the fuel gas
supply manifold hole 82a and the fuel gas exhaust manifold hole 82b,
respectively.

[0051] As illustrated in FIGS. 6 and 7, the insulating collar member 84a
integrally has a tubular portion 88 to be inserted in the oxidant gas
supply manifold hole 80a, and a flange portion 90 with a larger dimension
provided at one end of the tubular portion 88. The tubular portion 88 has
an approximately triangular shape (or an approximately trapezoidal shape)
corresponding to the inner shape of the oxidant gas supply manifold hole
80a, and is disposed with a space secured in the oxidant gas supply
manifold hole 80a. It is to be noted that the tubular portion 88 may be
in direct contact with the inner surface of the oxidant gas supply
manifold hole 80a.

[0052] An front end 88a of the tubular portion 88 is exposed to the
outside from the outer surface of the end plate 18b, and an O-ring (outer
circumferential surface sealing member) 92, which is a radial seal, is
arranged and disposed along a circumferential groove 88ad on the outer
circumference of the front end 88a. The O-ring 92 has an approximately
triangular shape or an approximately trapezoidal shape. It is to be noted
that the O-ring 92 may be disposed in, for example, a groove 100d which
is formed on the inner peripheral surface of the below-described oxidant
gas supply manifold 100 (see FIG. 7).

[0053] At least one, for example, two positioning holes 94 are formed in
the flange portion 90. A positioning pin 96 is inserted in each of the
positioning holes 94, and is inserted in a positioning hollow 98 which is
formed in the end plate 18b. As illustrated in FIG. 7, the flange 90 of
the insulating collar member 84a is in contact with the end surface of
the end plate 18b, and is pressed and held, for example, by the first
sealing member (end face sealing member) 40a of the first separator 22.

[0054] The insulating collar member 84b, 86a, 86b are formed similarly to
the above-described insulating collar member 84a, and the same components
are labeled with the same reference symbols, and detailed description
thereof are omitted.

[0056] As illustrated in FIG. 7, the oxidant gas supply manifold 100 is
provided with a connecting hole 100a, in which the front end 88a of the
tubular portion 88 provided in the insulating collar member 84b fits. The
connecting hole 100a has an opening with an approximately triangular (or
approximately trapezoidal) cross section, and the inner circumferential
surface of the connecting hole 100a is in contact with the O-ring 92, and
thus the tubular portion 88 is slidably disposed against the connection
hole 100a.

[0057] The screw 76 is inserted in a hole 100c which is formed in a flange
portion 100b provided on the outer circumference of the oxidant gas
supply manifold 100, and the end of the screw 76 is screwed in the tapped
hole 78 formed in the end plate 18b.

[0059] The operation of the fuel cell stack 10 with the above
configuration will be described hereinafter.

[0060] First, an oxidant gas such as an oxygen containing gas is supplied
to the oxidant gas supply manifold 100 of the end plate 18b as
illustrated in FIGS. 6 and 7, and a fuel gas such as a hydrogen
containing gas is supplied to the fuel gas supply manifold 104 as
illustrated in FIG. 6. In addition, a cooling medium such as pure water,
ethylene glycol, or oil is supplied to the cooling medium supply manifold
72 of the end plate 18a as illustrated in FIG. 1.

[0061] Thus, as illustrated in FIG. 7, an oxidant gas is introduced into
the oxidant gas passage 32 of the first separator 22 from the insulating
collar member 84a through the oxidant gas supply communication hole 26a.
As illustrated in FIG. 3, the oxidant gas, while moving in the arrow C
direction along the oxidant gas passage 32, is supplied to the cathode
electrode 44 included in the electrolyte membrane-electrode assembly 20.

[0062] On the other hand, a fuel gas is introduced into the fuel gas
passage 34 of the second separator 24 from the insulating collar member
86a through the fuel gas supply communication hole 28a as illustrated in
FIG. 6 (see FIG. 3). The fuel gas, while moving in the arrow C direction
along the fuel gas passage 34, is supplied to the anode electrode 46
included in the electrolyte membrane-electrode assembly 20.

[0063] Consequently, in the electrolyte membrane-electrode assembly 20,
the oxidant gas supplied to the cathode electrode 44 and the fuel gas
supplied to the anode electrode 46 are consumed by an electrochemical
reaction in an electrode catalyst layer, and thus electric power is
generated.

[0064] Subsequently, the oxidant gas which has been supplied to the
cathode electrode 44 and consumed is discharged in the arrow A direction
along the oxidant gas discharge communication hole 26b. On the other
hand, the fuel gas which has been supplied to the anode electrode 46 and
consumed is discharged in the arrow A direction along the fuel gas
discharge communication hole 28b.

[0065] As illustrated in FIGS. 1 and 3, a cooling medium is supplied from
the insulating collar member 58a to the cooling medium supply
communication hole 30a, and is introduced into the cooling medium passage
36 between the first separator 22 and the second separator 24 and flows
in the arrow C direction. The cooling medium, after cooling the
electrolyte membrane-electrode assembly 20, is discharged into the
cooling medium discharge communication hole 30b.

[0066] In the above case in the first embodiment, for example, as
illustrated in FIG. 5, the insulating collar member 58a is inserted in
the cooling medium supply manifold hole 54a, and the tubular portion 60
included in the insulating collar member 58a is in slidably contact with
the inner circumferential surface of the cooling medium supply manifold
(outer manifold member) 72 via the outer circumferential surface sealing
member, i.e., the O-ring (radial seal) 64.

[0067] Thus, with the adjustment of the thickness of the spacer member 19,
even when a positional variation in the stacking direction occurs inside
the fuel cell stack 10, the inner circumferential surfaces of the tubular
portion 60 and the cooling medium supply manifold 72 are self-adjustable
for the positional variation because of the sliding effect of the O-ring
64.

[0068] Therefore, a plurality of insulating collar members 58a with
different dimensions do not need to be produced each time when the
thickness of spacing member 19 varies, for example. Consequently, the
following effect is obtained: a desired sealing capability can be
achieved by using a single insulating collar member 58a which can be
favorably mounted to the end plate 18a, in a simple and cost effective
configuration.

[0069] It is to be noted that the effect similar to that of the
above-described insulating collar member 58a may be obtained using other
insulating collar members 58b, 84a, 84b, 86a, and 86b.

[0070]FIG. 8 is a perspective view of an insulating collar member 120
included in a fuel cell stack according to a second embodiment of the
present disclosure.

[0071] The insulating collar member 120 integrally has a tubular portion
122, and a flange portion 124 with a larger dimension provided at one end
of the tubular portion 122. The tubular portion 122 has a circular
cross-sectional shape corresponding to the circular cross-sectional shape
of the fluid manifold hole 128 of the end plate 126.

[0072] An front end 122a of the tubular portion 122 is exposed to the
outside from the end surface of the end plate 126, and an O-ring (outer
circumferential surface sealing member) 130, which is a radial seal, is
arranged and disposed along a circumferential groove 122ad on the outer
circumference of the front end 122a. The O-ring 130 has a circular shape.
It is to be noted that the O-ring 130 may be provided on a groove (not
illustrated) which is formed along the inner circumferential surface of
the fluid manifold hole 128.

[0073] In the second embodiment having the above configuration, the O-ring
130, which is a radial seal, is disposed outwardly of the tubular portion
122 of the insulating collar member 120. Therefore, the effect similar to
that of the above-described fuel cell stack 10 according to the first
embodiment is obtained. It is to be noted that in the first and second
embodiments, the insulating collar members 58a, 58b in an oval shape
(elliptical shape), the insulating collar members 84a, 84b, 86a, and 86b
in an approximately triangular shape (or approximately trapezoidal
shape), and the insulating collar member 120 in a circular shape are
used, however, the shapes of the insulating collar members are not
limited to the above shapes.

[0074] A fuel cell stack according to the embodiment includes: a stacked
body in which a plurality of fuel cells are stacked, each of the fuel
cells including an electrolyte-electrode assembly having an electrolyte
and a pair of electrodes being disposed on both sides of the electrolyte,
and a pair of separators between which the electrolyte-electrode assembly
is sandwiched; a pair of terminal plates; a pair of insulating plates; a
pair of end plates; and an insulating collar member. Both ends of the
stacked body in the stacking direction are respectively provided with the
terminal plates, the insulating plates, and the end plates, and a fluid
manifold hole is formed in at least one of the end plates, the fluid
manifold hole for supplying or discharging, to an outer manifold member,
a cooling medium or a reactant gas which flows in the stacking direction.

[0075] The fuel cell stack according to the embodiment includes an
insulating collar member which is disposed to a fluid manifold hole, and
the insulating collar member has a tubular portion to be inserted in the
fluid manifold hole, and a flange portion to be disposed at one end of
the tubular portion. The flange portion is in contact with an insulating
plate via an end-face sealing member, and the other end of the tubular
portion projects to the outside of the fluid manifold hole, and is in
slidably contact with the inner circumferential surface of an outer
manifold member via an outer circumferential surface sealing member.
Thus, even when a positional variation in the stacking direction occurs
inside the fuel cell stack, the inner circumferential surfaces of the
tubular portion and the outer manifold member are self-adjustable for the
positional variation because of a sliding effect of the outer
circumferential surface sealing member. Consequently, a plurality of
insulating collar members with different dimensions do not need to be
produced, and an insulating collar member has a desired sealing
capability and can be favorably mounted to an end plate in a simple and
cost effective configuration.

[0076] In the fuel cell stack according to the embodiment, a spacer member
which adjusts the thickness of the fuel cell stack in the stacking
direction is preferably interposed between the end plate and the
insulating plate.

[0077] Obviously, numerous modifications and variations of the present
invention are possible in light of the above teachings. It is therefore
to be understood that within the scope of the appended claims, the
invention may be practiced otherwise than as specifically described
herein.